Preparation And Properties Of Glass Fiber Reinforced Phenolic Molding Compounds

In this paper, the preparation, structure and properties of the phenolic molding compounds reinforced with glass fiber (GF) and glass fiber/cotton fiber (CF) hybrid fibers (GF/CF) were studied systematically. The influence of different surface treatments, length and content of fiber, and blend resin matrix on the properties of phenolic molding compounds were analyzed. The research work is useful to develop new phenolic molding compounds and optimize their properties.Surface treatment had great influence on the properties of phenolic molding compounds reinforced with fibers. Alkali-thermal, silane coupling agent K.H-792 treatments were used to treat the surface of glass fibers and cotton fibers. The results showed that these treatments could improve the reinforcement of GF and CF to phenolic molding compounds. The properties of phenolic molding compounds could be improved significantly by incorporation of GF compared with wood powder, exhibited higher impact strength than CF.Length of GF had little influence on the properties of phenolic molding compounds, but that of CF had great influence on the properties of phenolic molding compounds. Longer CF had more advantages to improve the mechanical and thermal properties of phenolic molding compounds than shorter CF, but it would cause lower electricity and water resistivity.Substituting part of wood powder, GF (alkali-thermal treated) was used to reinforce phenolic molding compounds. The results showed that with the increasing of GF contents, the flexural strength and notched impact strength of composites increased at first and then stabilized, the heat distortion temperature increased, and water absorption dropped, electric strength presented slightly raising trend.Blend resin matrix of novolac and resole was used to substitute the traditional novolac matrix to prepare composite reinforced with GF. The results show that curing system had great influence on the properties of composite. With the precent of resole increased in blend system, the mechanical and thermal properties increased first and then dropped. The observation of SEM showed that it had better adhesion in resole and blend system than novolac system.Hybrid fibers of GF and CF were treated with silane to reinforce novolac phenolic molding compounds. The results showed that as the hybrid ratio of GF/CF increased, the impact strength, heat distortion temperature and volume resistivity of composite presented a decreasing trend, but the impact strength and water absorption of composite presented an increasing trend. The micrographs of SEM revealed that the fracture mechanism of composites reinforced with GF was typical rigid fracture, and the fracture mechanism of composites reinforced with CF was typical toughness fracture. It was observed that GF/CF hybrid fibers dispersed homogeneously and arranged alternatively on the fracture surface.Hybrid fibers of GF and CF were treated with silane to reinforce blend phenolic molding compounds. The results showed that as the hybrid ratio of GF/CF increased, the impact strength, heat distortion temperature and volume resistivity of composite presented a decreasing trend, but the impact strength and water absorption of composite presented an increasing trend.